Blinding Shield would be a new paladin ability that would come with Cataclysm, learned at level 81. It was first announced in the Cataclysm paladin preview.[1][2] However it seems to have been removed and replaced with [Inquisition] as the level 81 ability.

Blinding Shield would damage and blind all nearby targets. This effect might have ended up only damaging those facing the paladin's shield, in a manner similar to Eadric the Pure's ability Radiance in Trial of the Champion. The Holy tree would have a talent to increase the damage and critical strike chance, while the Protection tree would have a talent to make this spell instant cast. 2-second base cast time. Would require a shield.

While scrapped in Cataclysm, it seems Blizzard gave it a new chance in Mists of Pandaria as " [Blinding Light]", a level 87 spell which disorients targets in a 10 yard radius for 6 seconds.